The present invention relates to an internal combustion engine in which there is a compression boost for the fuel-air mixture directed to the combustion chamber of the cylinder. According to the invention, the internal volume of engine block, including the crank case, serves as a compression chamber in which air is compressed by the reciprocating action of the pistons.
There is an ongoing need for increasing the power from small displacement internal combustion engines. This can be readily accomplished, for example, by turbocharging or supercharging, however, the problem is complicated by the changing requirements for pollution control of the exhaust from such engines.
There have been disclosed in the prior art, internal combustion piston-type engines in which the fuel-air mixture from a carburetor is passed into the crankcase of the engine where it is compressed. The compressed fuel-air charge is then conducted via manifolds into the combustion chambers.
Such systems, while effective in increasing the power of the engine by compressing the fuel-air mixture, do not appear to solve the problem of reducing pollution control, since passing a fuel-air mixture through the engine block mixes it with oil mist which results from the lubrication of the crankshaft journals, oil pan, etc. Introducing this oil into the combustion chamber to be burned adds to the pollution of the exhaust gases.
Therefore, there is a need in the art to provide an internal combustion engine in which power can be enhanced by compression of the charge entering the combustion chamber, yet still meeting the increasingly stringent pollution control standards. Furthermore, there is a need to accomplish this in a technically simple manner, preferably by avoiding use of expensive catalysts (which must be replaced) which use precious metals, and avoiding delicate electronic computer-controlled equipment whose longevity is questionable in the stringent environment of an internal combustion engine.
In accordance with the present invention, and as a principal embodiment thereof, the present invention provides a four-stroke reciprocating piston-internal combustion engine comprising a cylinder block having a plurality of cylinders, where each of the cylinders accommodates a piston slidably received therewithin. One side of each of the pistons defines a combustion chamber and the other side, to which a connecting rod is affixed, serves to compress the volume of air within the crankcase. Each combustion chamber may be in communication in a conventionally timed manner through a first valve means with a source of a fuel-air mixture (such as a carburetor or fuel injection system) to admit this mixture into the chamber, and further in communication in a timed manner through a second valve means with an exit port to withdraw exhaust gases from the combustion chamber. The connecting rods connect the pistons to the crankshaft which is enclosed by the engine block or combination of an engine block and crankcase which is sealed, usually to the bottom of the engine block. The engine block also accommodates journal supporting means for accommodating the crankshaft and crankshaft bearings. The internal portion of the block may also have internal walls, also providing additional journal-supporting means for the crankshaft and crankshaft bearings. Depending on the configuration of the engine, the block may also accommodate journal-supporting means for camshafts and camshaft bearings. The bottom of the crankcase may, but does not necessarily have to include an oil pan at its lowermost portion. An air and fuel intake system is coupled to the cylinders, usually by a manifold system leading from one or more carburetors or a fuel injection system. The present invention provides an improvement to such an internal combustion engine by providing sealing plates to substantially form an air-tight seal between the oil pan, if present, and the interior volume of the engine to thereby define a compression chamber comprising the interior of the crankcase and the volume within the engine block in communication with the crankcase and bottom of the pistons. The primary purpose of the sealing plate(s) is to prevent oil in the oil pan from mixing with the interior volume of the crankcase (which is a compression chamber) so as not to contaminate the air passing through the crankcase with oil. No fuel or fuel vapors are introduced into this interior volume. To utilize the crankcase (sealed from the oil pan) as a compression chamber, at least one one-way valve means is adapted on the engine block in communication with the compression chamber which allows air to be admitted from the atmosphere into the compression chamber. Such a one-way valve means is preferably a reed valve. The desired pressure to be attained within the compression chamber can be selected by adjusting the pressure on the closure of the reed valve.
In the preferred embodiment shown in the attached figures, there is shown a flat horizontally opposed four cylinder engine in which there are two banks of two cylinders. The two cylinders (one on each of the banks) which directly oppose each other simultaneously are on a downward stroke thereby compressing the air within the chamber. As shown in the preferred embodiment, there are two distinct compression chambers, so that the four cylinders do not counteract each other, i.e., when two opposing cylinders are on their downward (inward) stroke one volume of air is compressed which is separate from the volume of air which is compressed when the other two opposing cylinders are on their downward stroke. The separation between the two volumes of air is accomplished by an internal wall extending from the interior of the block of the engine which also provides additional journal-supporting means for the crankshaft.
After compression of the air in the compression chamber (which does not contain any fuel or oil) a one-way valve means adapted on the block is provided which releases the compressed air from the compression chamber toward the air and fuel intake system. Preferably the compressed air is first retained in a compression reservoir from which the air can be regulated through a valve means such as a butterfly valve and directed into the intake manifolds or other equivalent means of introducing the fuel and air into the combustion chambers.
When adapted to a conventional four-stroke internal combustion engine, by providing a sealing plate(s) between the oil pan and crank case, the engine must further be provided with a method for lubricating the crankshaft journals and camshaft journals if the camshafts are disposed within the compression chamber. This lubrication, however, must be provided in a way so as not to allow oil droplets or mist to be mixed with the air in the compression chamber. Therefore, lubricating channels are provided according to the present invention in the journal-supporting means for the crankshaft and camshaft (if necessary). Liquid lubricant is flowed from an oil pump means through the lubricating channels and then directed through a channel to an oil pan located below the sealing plate. In this manner the lubricating fluid which lubricates the journals does not come in contact with the compression chamber, but still provides adequate lubrication for the journals.
It is contemplated that although the above method for lubricating the crankshaft and camshaft journals will probably not allow contact of the oil with the compression chamber, during high RPM operation of the engine and particularly after there is much engine wear, there is a possibility of seepage of small amounts of oil into the compression chamber, such as by ring wear around the pistons. Therefore to continue to maintain the low pollution emission from the engine, a filtering means may be provided adjacent to the second valve means (through which the compressed air exits the compression chamber) to filter any solid or liquid particulate matter which may be present in the compression chamber.
To circulate the lubricating oil within the engine described in the preferred embodiment, oil is withdrawn through a line directly from the oil pan through the conventional oil pump which is adapted to the engine and recirculated (after passage through an oil cooler, if present) directly to an input line to the lubricating channels for the crankshaft and camshaft journals.
The above description of the invention may be provided to include the described features during the original manufacture of the engine. However, it is further contemplated that the above modifications may be made to retrofit existing engines.